Since the methods of digitally processing audio and the methods of digitizing video are different and since they correspond to different processing times, it is always necessary to synchronize the sound and the image produced by an audio/video source and transmitted to an audio/video playback device.
Thus, with reference to FIG. 1, an original audio/video signal Sav is transmitted by a decoder unit 1 (also known as a “set-top box”) to a TV set 2, in this example via a cable 3 of high-definition multimedia interface (HDMI) type. The original audio/video signal Sav is subjected to digital audio decoding processing 4, and to video decoding processing 5, respectively producing an audio signal and an image signal Si. After the digital audio decoding processing 4, the audio signal is also subjected to synchronization processing 6 so as to be synchronized with the image signal Si. This produces an audio signal Sa1. The image signal Si and the audio signal Sa1 are then played back respectively by the screen of the TV set 2 and by the internal loudspeaker of the TV set 2.
The synchronization processing 6 is set either to be constant and specific to the TV set 2, or else is manually adjustable “by ear” by the user, or else is based on measuring a video delay by using a light source and a light sensor.
Nevertheless, with reference to FIG. 2, when a loudspeaker is used that is external to the TV set 2, e.g. a sound bar 8, the delay Δt induced by the digital audio decoding processing 9 in order to produce the audio signal Sa2 that is to be played back by the sound bar 8 is not necessarily identical to the delay induced by the digital audio decoding processing 4 for producing the audio signal Sa1 that is to be played back by the internal loudspeaker of the TV set 2. It is therefore appropriate to synchronize these audio signals Sal and Sa2 so as to avoid the occurrence of a disagreeable sound offset.